Data communications systems provide fixed or wireless two-way data communications enabling users, such as mobile professionals, to communicate almost instantly with business associates, customers, family members, and friends. A typical wireless data communications system comprises user terminals, network gateways, network controllers and base stations. A typical base station covers a small zone of several kilometers in radius and forms a data communications system with user terminals. A network controller typically controls communications of an area which covers a plurality of base stations. A host computer is generally installed by the user and executes various applications.
Data communications systems are used for wireless e-mail and messaging, news retrieval, and other information services. Additional applications can be developed that allow users wireless access to corporate and public information systems.
Today, information can be accessed exactly when and where it is needed, and time sensitive messages can be sent and received wherever the user goes. However, when a host computer is down, the data communications network is unable to deliver messages from the user terminals to the problem host computer. As a result, data communications network performance can be adversely affected. If the affected applications continue to send data from the user terminals to the problem host computer, then all users (including those not associated with the problem host computer) may observe longer message transit times.
Network performance can also be adversely affected by host computers that are slow to respond to messages sent from user terminals. As with host computers that are down, all users may observe degraded performance even if they belong to a different group of user terminals.
Further, congestion can occur when messages deplete a critical resource such as buffer space. Buffer space is an area of memory allocated for buffering purposes. In data communications networks, host computers that are down and host computer that are slow can lead to holding messages at the interfaces between network components.
As a result, there is a need for an improved method for managing sessions and performing end-to-end session control in a data communications system. It would be desirable to protect the data communications network in situations where faults connected to a particular host computer do not affect all user terminals and their users.
______________________________________ Glossary of Acronyms ______________________________________ DTE Data Terminal Equipment HUM Host User Mapping NAK-SDU Negative acknowledgment - Service Data Unit RD-LAP Radio Data-Link Access Protocol RNC Radio Network Controller RNG Radio Network Gateway RPM Radio Packet Modem SDU Service Data Unit ______________________________________